Pharmaceutical removal by ion exchange process

Abstract

Understanding the interaction of pharmaceuticals with common ion exchange resin used in drinking water treatment plants and sewage water treatment plants is essential to evaluate their routes and behavior in the aquatic environment. The ion exchange of four pharmaceuticals, acetaminophen (ACE), nalidixic acid (NAL), nofloxacin (NFC), and 17-alpha-ethinyl estradiol (EE2), has been investigated in the laboratory using batch experiments at neutral pH range. Anion exchange and cation exchange resins are used as sorbent materials. The preliminary tests showed that acetaminophen, which is in neutral form and has the highest water solubility (14,000 mg/L at 25ํC), was sorbed onto both of ion exchange resins. While nalidixic acid, which has one carboxylic functional group, exchanged with anion exchange resin but no significant ion exchange process with cation exchange resin. Norfloxacin exchanged with both resins. 17 [alpha]-ethinyl estradiol, the most hydrophobic molecule, was similar to acetaminophen, it was sorbed onto anion exchange resin and cation exchange resin. For equilibrium time studies, Acetaminophen on anion exchange resin and cation exchange resin showed that equilibrium was reached within 3 hours. While nalidixic acid on anion exchange resin required 6 hours to achieve the equilibrium. Norfloxacin on both resins reached equilibrium at 1 day. 17 [alpha]-ethinyl estradiol on anion exchange resin and cation exchange resin were used 12 hours and 6 hours, respectively. A Langmuir isotherm was used to fit to ion exchange data of nalidixic acid and norfloxacin but for acetaminophen and 17 [alpha]-ethinyl estradiol were fitted with Linear isotherm. The sorption coefficient and maximum adsorption capacity of nalidixic acid on anion exchange resin were 94 L/g and 1.11 mg/g, respectively. The sorption coefficient of acetaminophen on anion exchange resin and cation exchange resin were 0.0228 L/g and 0.0041 L/g, respectively. The sorption coefficient of norfloxacin on anion exchange resin was 42 L/g and maximum adsorption capacity was 0.93 mg/g, on cation exchange resin, the sorption coefficient was 37 L/g and maximum adsorption capacity was 27.67 mg/g. The sorption coefficient of 17 [alpha]-ethinyl estradiol on anion exchange resin was 0.8096 L/g and on cation exchange resin was 0.0510 L/g. For anion competition studies, sulfate ion competed with nalidixic acid and norfloxacin more than did bicarbonate ion and competition increased with increasing concentration of these two ions.